Method of and apparatus for rolling flat strip

ABSTRACT

THE DISCLOSURE OF THE PRESENT INVENTION RELATES TO A 4-HIGH STRIP ROLLING MILL, WHEREIN THE WORK ROLLS ARE OFFSET AND ON OPPOSITE SIDES OF A PLANE CONTAINING THE AXES OF THE BACKUP ROLLS OF THE MILL. THE STRIP IS CAUSED TO ALTERNATELY WRAP AROUND A PORTION OF EACH WORK ROLL IN A MANNER TO EFFECT AN OVERALL REDUCTION IN THE THICKNESS OF THE STRIP BY COMPRESSION FROM THE ROLLS, AND AT THE SAME TIME SUBJECT THE OPPOSITE SIDES OF THE STRIP AS THEY COME INTO CONTACT WITH THE WORK ROLLS ALTERNATELY O A TENSION FORCE SUFFICIENT TO ELONGATE BY TENSION THE OPPOSITE SIDES OF THE STRIP. THE DISCLOSURE INCLUDES A ROLL HEATING AND COOLING SYSTEM FOR VARYING THE CROWN OF THE WORK ROLLS AND HENCE, THE AMOUNT OF THE TENSION FORCE ALTERNATELY IMPOSED ON THE OPPOSITE SIDES OF THE STRIP IN ORDER TO CHANGE THE DEGREE OF ELONGATION TRANSVERSELY ACROSS THE STRIP.

Nov. 2, 1971 c. s. SHUMAKER 3,616,659

METHOD OF AND APPARATUS FOR ROLLING FLAT STRIP Filed June 13, 1969 2 Sheets-Sheet 1 mvmm m.

CHARL 5 5. Sl/UMA/(ER L BY fig? ATTO/Q/VEV.

Nov. 2, 1971 c. s. SHUMAKER 3,616,669

METHOD OF AND APPARATUS FOR ROLLING FLAT STRIP Filed June 13, 1969 2 Sheets-Shoot 2 I P 6Q INVENTOR.

6 (HA/@155 5. SEQ/MAKE)? ATTOR/VEV.

United States Patent O1 fice 3,616,669 Patented Nov. 2, 1971 Filed June 13, 1969, Ser. No. 833,045 Int. Cl. B2111 27/06 U.S. Cl. 72-200 6 Claims ABSTRACT OF THE DISCLOSURE The disclosure of the present invention relates to a 4-high strip rolling mill, wherein the work rolls are olfset'and on opposite sides of a plane containing the axes of the backup rolls of the mill. The strip is caused to alternately wrap around a portion of each work roll in a manner to effect an overall reduction in the thickness of the strip by compression from the rolls, and at the same time subject the opposite sides of the strip as they come into contact with the work rolls alternately to a tension force sufficient to elongate by tension the opposite sides of the strip. The disclosure includes a roll heating and cooling system for varying the crown of the work rolls and hence, the amount of the tension force alternately imposed on the opposite sides of the strip in order to change the degree of elongation transversely across the strip.

This invention relates to a method of and apparatus for processing strip-like material; for example, the rolling of steel or aluminum strips.

SUMMARY OF INVENTION In the rolling of thin metallic strip, such as mild carbon steel and alloy aluminum, one of the much sought-after quality characteristics is a dead-soft flat product. By flat is meant a sttrip relatively free from buckles, waves, etc., which frequently occur in the rolling process due primarily to an incorrect roll contour being employed. In many cases, in order to obtain the requisite flatness in the product, the strip, after the final rolling step, is passed through a separate processing station where it is leveled and/r stretched. While in all but the worst conditions this separate processing strip usually produces the required flatness, it, notwithstanding, adds significantly to the cost of producing quality strip, not to mention the large capital outlay involved.

In light of this it is the object of the present invention to provide a method of and apparatus for producing a strip characterized by substantial flatness obtained not by a separate processing strip, but as a function of the reducing, tempering skin pass rolling or leveling of the strip.

It is a further object of the invention to provide a method and apparatus for producing a fiat metallic strip, where the strip is passed between a pair of offset rolls to subject the strip in one case to an overall reduction by compression from the rolls or in a second case to a compression below the yield point of the strip; and wherein the opposite sides of the strip are alternately subject to a tension force su'fficient to alternately elongate the opposite sides of the strip; and wherein the crown of at least one of the rolls is varied to vary the degree and application of tension transversely of the strip; and, hence, the elongation to correct for the non-flatness in strip issuing from the rolls.

It is a still further object of the invention to provide a rolling mill having a pair of work rolls arranged with their axes on opposite sides of a common vertical plane and so disposed that the workpiece is caused to wrap around a portion of the rolls in a manner that the rolls both reduce the overall thickness of the strip by compression and at the same time impose tensions on the opposite sides of the strip sufficient to elongate the strip and means for varying the contour of at least a section of one of the rolls to vary the elongation in a desired transverse portion of the strip to correct for non-flatness in the strip issuing from the rolls.

These objects as well as other features and advantages of the present invention will be better appreciated when the following description is read along with the accompanying drawings of which:

FIG. 1 is an elevational section view of a 4-high mill incorporating the present invention,

FIG. 2 is a diagrammatic plane view of one form of the crown control apparatus that forms part of the invention,

FIG. 3 is a perspective view of one of non-flat condition of a strip that is to be corrected by the practice of the invention,

FIG. 4 is a partial view of the work rolls of FIG. 1 illustrating by the solid lines in exaggerated form the roll condition that creates the non-flatness illustrated in FIG. 3 and by the dotted lines what correction must be made to remove the non-flatness.

FIG. 4a is a sectional view taken on lines 4a4a of FIG. 4, illustrating in solid line the rolls of FIG. 4 and in dotted lines what takes place by the practice of the present invention in correcting for the non-fiat strip condition,

FIG. 5 is a perspective view of a second non-flat condition of a strip,

FIG. -6 is a partial view of the work rolls of FIG. 1 illustrating by the solid line in exaggerated form the roll condition that creates the non-flatness shown in FIG. 5 and by dotted lines what correction must be effected to correct for the non-flatness, and

FIG. 6a is a sectional view taken on lines 6a-6a of FIG. 6 illustrating in solid lines the rolls of FIG. 6 and in dotted lines what takes place by the practice of the present invention to correct for the non-flat strip condition.

In order to assist in a better understanding of the invention in the following description, certain definitions will now be given. As used hereinbefore and subsequently, the terms:

(a) Buckle describes a deflection of the strip at its center, which, while they usually take the form of either a down-buckle or an up-buckle, on certain occasions they alternate as downand up-buckles or vice-versa,

(b) uniform wave describes one or both edges of the strip where the deflections of the strip take the form of a sine curve,

(0) scallop is a condition on one or both edges, but

otherwise is similar to the buckled condition, and

(d) by a crown is meant the increase or decrease of a radial section of the roll body in engagement with the strip.

The fundamental purpose of the present invention has to do with a method of and apparatus for rolling metallic strip in a manner whereby, simultaneously with the reductions caused by compression from the work rolls, a given section of the strip being reduced by compression is subject also to a tension force in a manner that the opposite sides are alternated and, if desirable, differentially elongated and wherein the degree and application of the tension force transversely of the strip can be accurately varied by adjusting the crown of one or more of the rolls so that the tension force can be applied with reference to the extent and exact nature of the non-fiat characteristic of the strip, i.e., whether it is a wave, buckle, or scallop and, as to the latter two, the direction of deflection of the strip.

With reference to FIG. 1, there is illustrated diagrammatically a rolling mill housing 11 which receives a pair of backup rolls 12 and 13 for supporting work rolls 14 and 15; thus, constituting the mill a 4-inch mill. It will be appreciated that the rolls are received in and supported by customary bearing chock assemblies and that the upper rolls 12 and 14 are adjustable within the housing towards and away from the lower rolls 13 and 15 by a screw-down mechanism, according to well-known practice. The bearing chock assemblies of the work assemblies 14 and 15 are so constructed and arranged with respect to the housing and/or the bearing chock assemblies of the backup rolls 12 and 13 that they are held in a predetermined offset relationship with respect to a vertical plane containing the axes of the backup rolls 12 and 13. The amount of offset is variable to meet the many different rolling conditions of a given mill. FIG. 1 shows this ofiset condition in an exaggerated form as it does with respect to the strip passing between the work rolls 14 and 15. On the entry side of the mill, as illustrated in FIG. 1, which side is indicated by the arrow, there is mounted for each backup rollwork set a series of nozzles 16 and 17, respectively.

As best shown in FIG. 2, these nozzles are adapted to admit into the gap formed by the roll sets, and continuously along such gap, a discharge of either a heating or cooling medium, say, for example, water. The nozzles are arranged so that the outer two constitute a pair 16a as do the next adjacent inner ones 16b, while the center one 160 is independent of the other two sets. Each set of sprays as well as the center spray 160 is connected to valves 18, 19 and 21 which, in turn, through headers 22 and 23 are connected to heat exchangers in the form of a medium cooling unit 24 and medium heating unit 25; the heat exchangers, in turn, being connected to a pumping system and reservoir not shown.

The two sets of views, i.e., FIGS. 3, 4 and 4a and FIGS. 5, 6 and 6a are designed to illustrate both the reduction of the strip by compression from the work rolls 14 and 15 and the correcting effect of the elongation by controlling the crown of the rolls for two different strip non-flat conditions.

As noted previously, it is an important feature of the present invention to provide for the control of the elongation so that one side of the strip can be elongated more or less than the other side and with precise exactitude. The final product can, accordingly, be rolled flat or, if desired, internally bowed. This objective is realized in the action that takes place when the strip is caused to alternately pass around, first, the top work roll 14 and, then, the bottom work roll 15. Because the gap between the work rolls 14 and 15, i.e., the distance between their cooperative surfaces as measured by a line drawn between their two axes is less than the incoming thickness of the strip, a strip is reduced by the compression or resistance generated by the work rolls 14 and 15. At the same time the reduction is being accomplished by compression from the work rolls, the encircling effect of the strip with respect to the work rolls impose differential tensions on the strip with respect to the two opposite sides, which differential tensions alternate from one side to the other depending on whether the side is caused to be placed under compression or tension as it is forced to wrap around the work rolls. By recognizing that the degree of the elongation can be varied along the face of the roll, i.e., along its axis, by varying the crown of the roll the application and degree of elongation can be related to either the center or edge of the strip depending where the non-flatness lies. Moreover, with respect to a non-flat condition in the form of buckles, where they generally consist of an upward or downward deflection from the body of the strip, by increasing the crown on one roll and allowing the crown to remain unchanged on the other or reducing the crown on the other roll, the elongatiorrs can be controlled to be related exactly to the direction of deflection of the strip.

These principles and their application as to a wave condition in the strip are best appreciated in referring to FIGS. 3, 4 and 4a where there is shown a greatly exaggerated representation of the rolling action between the work rolls 14 and 15. It should be noted, first, that the hard-line representations of FIGS. 4 and 4a are designed to portray a condition Where the work rolls 14 and 15 are crowned to the same extent and that under these conditions a wave is formed in the strip issuing from the rolls. As noted before, this wave is a result of the rolls not being properly crowned for the particular rolling load generated by the reduction being taken. The waved condition will be observed either by the operator or by some apparatus designed to 'detect the presence of a wave. The operator examining this condition has the option of either increasing the crown in the center of the Work rolls 14 and 15 or decreasing the crowns at the edges or doing both, but in a lesser amount.

Whatever the choice may be in this regard, he needs simply to operate the valves 18, 19 and 21 of each spray system 16 and 17 to accomplish the desired end.

An application of the coolant or heating medium in the above manner with respect to changing the crown at the center of the roll or rolls 14 and 15 is illustrated in dotted lines in FIGS. 4 and 4a, where it is shown that the rolls 14 and 15 have increased in diameter at the centers while the ends remain unchanged.

FIGS. 5, 6 and 6a are addressed to a buckled condition where the buckles deflect upwardly. The general analysis is similar to the wave condition described with reference to FIGS. 3, 4 and 4a, except that with the buckled condition, the operator of the apparatus employed must also determine the direction of the deflection of the buckles-in this case upward deflection.

Under these conditions the operator has the option to either decrease the crown at the center of the roll 15 or increase the crown at the center of the roll 14 and increase the crown of the rolls 14 and 15 at these ends by operation of the valves 18, 19 or 21.

In order to better appreciate what actually takes place, FIG. 4a has been provided with certain letter identifications for the purpose of allowing ready reference to the various arcs formed by the engagement of the strip with the rolls 14 and 15. In this connection let it be assumed that the offset between the axes of the work rolls 14 and 15 is /2 inch with a work roll radius of 9 inches and the angle of CD of 3.2 degrees having a sine of .0556, the length of the are where t is the incoming thickness of the strip, which is the same as the sine of the arc CD; likewise, the length of the arc DEBF where t is the final thickness of the strip, and is the same as the sine of the first angle. Therefore, it follows that the elongation of the bottom surface AB is 5 /2 percent more than the top surface CD. The elongation of the top surface DE is 5% percent more than the bottom surface BF. By controlling the crown of the work roll 14, very accurate adjustments can be made in the relative tension in the bite to effect a control of the elongation of the strip across the width of the bottom side of the strip. Likewise, the contour of the bottom work roll 15 can be minutely adjusted and the differential tensions across the strip varied at the top side of the strip. This is illustrated in exaggerated form in FIG. 6a with respect to increasing the crown of the bottom roll 15 at the center of the roll. As shown, this increase causes a greater elongation on the opposite side of the strip as can be determined in noting the difference in the arcs CD and AB of FIG. 4a.

With reference to reduction rolling as distinguished from skin pass or temper rolling, in a given mill operation the overall reduction in the strip caused by compression from the work rolls will be substantially greater than the elongation imposed by the tension caused by the offset condition of the work rolls. In a reduction mill, reduction by compression may be of the order of -45 percent; whereas, the differential elongation between the top and bottom of strip would not exceed 5 percent.

In returning now to FIG. 2 and in order to better appreciate the extent of crown control obtained by the cooling and heating system illustrated, let it be considered that the valve 19 connected to the heat exchangers 24 and 25 delivering 100 F. and 150 F., respectively, valve 19 will deliver a medium temperature of 125 P. which represents the mean temperature of the discharge of the heat exchangers and that the medium issuing from valves 18 and 21 is also 125 F. If the particular non-flat condition is one of wavy edges, i.e., the edges are being overrolled by improperly crowned rolls, the valve 21 will be caused to emit fluid at 110 F. (80 percent at 100 F. +20 percent of 150 F.) and the valve 18 will be changed to emit fluid at 140 F. which represents (20 percent at 100 F. and 80 percent at 150 F.). This then represents 15 (.0O0006 2 (2 "+18" diameter)=.00009 Thus, the work rolls will decrease in their edges by the amount of .0075" and the center of the rolls will increase in diameter by a similar amount of .0075", making the total crown change of .015.

While for illustrative purposes a fluid cooling control system has been described, as will be appreciated by those skilled in the art, various other forms are available for controlling the crown of the rolls, for example, apparatus designed to bend either the work rolls or backup rolls by an external force.

As noted before, the method and apparatus of the present invention may be practiced to level the strip where no reduction is imparted by compression between the rolls. In referring again to FIG. 4a the elongation of the bottom fibers of the strip is caused by the bending action of the top roll 14, i.e., the strip side AB and the elongation of the top fibers of the strip is caused by the bending action of the lower roll 15, i.e., the side of the strip DE. The compression between points D and B is held below the yield strength of the material and hence is not suflicient to impart any reduction. The degree and application of the tension on one or both sides of the strip is similar to what has already been described above and is effected by the control of the crown or crowns of one or both of the rolls.

In accordance with the provisions of the patent statutes, I have explained the principle and operation of my invention and have illustrated and described what I consider to represent the best embodiment thereof.

I claim:

1. In a method of rolling flat metallic strip including the steps of:

passing the strip between a pair of Work rolls so that the strip is caused to alternately bend around one roll, then the other roll in a manner that the overall thickness of the strip is reduced by compression and the opposite sides of the strip are alternately subject to a tension force sufficient to assist in elongating the two opposite sides of the strip, and

2. In a method of rolling fiat metallic strip in accordance with claim 1, wherein the overall reduction of the strip imparted by compression of the rolls is appreciably larger than the amount of elongation of the strip by applying said differential tension.

3. In a method of rolling flat metallic strip in accordance with claim 2, wherein said amount of elongation on each side of the strip does not exceed 5 percent.

4. In a method of rolling flat metallic strip, including the steps of:

passing the strip between a pair of rolls which form a compression area with the strip and wherein the compression force of said rolls in said compression area does not exceed the yield strength of the strip.

causing the strip to alternately bend first around one of said rolls, then around the other of said rolls in a manner that one side of the strip is subject to tension and the opposite side of the strip is subject to compression during each alternate bending so that the sides of the strip are caused to elongate a controlled amount, and

dependent on the direction of deflection of a non-flat strip issuing from the rolls, selectively varying the crown of one or the other of said pair of rolls to vary differentially the said tension on the top or bottom of a transverse portion of the strip during the time said portion is subject to said compression force.

5. In a rolling mill adapted to roll flat strip having a pair of work rolls between which the metal strip is passed,

means for maintaining said rolls so that their axes are offset and spaced equally distant on the opposite side of a common vertical plane passing through said rolls. the relationship of the strip and the rolls being such that the strip is alternately caused to wrap around a portion of the rolls to both reduce the overall thickness of the strip by compression of the rolls and to subject the opposite sides of the strip that come into contact with the rolls to differential tension sufficient to elongate differentially the opposite sides of the Strip, and

separate means, dependent on the direction of deflection of a non-flat strip issuing from the roll, for selec tively varying the crown of one or the other of said pair of rolls to vary differentially the said tension on the top or bottom of a transverse portion of the strip during said reduction by compression of said portion.

6. In a rolling mill according to claim 5 wherein each work roll is backed up by a backup roll, and

means for mounting each backup roll so that their axes fall in substantially the vertical planes containing the aXes of their cooperative work rolls.

References Cited UNITED STATES PATENTS 2,095,733 10/1937 Coryell 72205 X 2,316,067 4/1943 Hickman 72-205 X 2,332,796 10/1943 Hume 72-205 X 2,526,296 10/ 1950 Stone 72-205 3,049,950 8/1962 Pearson 72-8 3,210,982 10/1965 Polakowski 72-237 X 3,213,655 10/1965 Reid 72-11 3,253,445 5/1966 Franck 72-205 X 3,334,508 8/1967 Martin 72-9 X 3,394,577 7/ 1968 Rastelli 72-242 MILTON S. MEHR, Primary Examiner US. Cl. X.R. 72-241 UNITED STATES PATENT OFFICE CERTIFICATE 0i CGRRECTION Patent No. 3,615,669 D te November 2, 1971 Inventor) Charles Storer Shumaker It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 38, attrip" should read strip Column 3, line 1, 4-inch" should read 4 high Column 3, line 19, after "work" should read roll Column 5, line 64, after "strip, and" should read dependent on the direction of deflection of a non-flat strip issuing from the rolls, selectively varying the crown of one or the other of said pair of rolls to vary differentially the said tension on the top or bottom oi a transverse portion of the strip during said reduction by compression of said portion Signed and sealed this 17th day of October 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOITSCHALK Attesting Officer Commissioner of Patents PC4050 USCOMM-DC scan-Pee U 5, GOVERNMENT PRINTING OFFICE ISIS O36633l, 

